Lift platforms are widely used in the construction industry to allow construction operators to gain access safely to locations at heights of typically up to about 20 meters or more above ground or floor level, and perform construction operations at those locations.
A lift platform usually includes a base unit, a lift mechanism including a boom arm and an operator cage mounted on the end of the arm. The base unit includes a drive motor and a hydraulic drive system for driving movement of the lift mechanism. The operator cage includes a control console allowing the operator to control movement of the cage.
As lift platforms are generally free standing, the base unit must be sufficiently heavy to ensure that the lift platform is stable at all times. Generally, the largest turning moment will occur when the boom arm is at its maximum extension to one side of the base unit and the operator cage is carrying its maximum permissible load. Typically, the base unit might have a weight in the range of 5-6 tonnes.
Some lift platforms, known as mobile lift platforms, are fitted with motorised wheels or tracks that allow the lift platform to be driven from one location to another. This is very useful as it allows the lift platform to be moved easily to new locations as required.
Sometimes, mobile lift platforms are used during the erection of multi storey (steel framed or other) buildings and are lifted by a tower crane onto each successive floor of the building as it is constructed. This allows the operator to take part in construction of the steel framework for the next floor. However, there is a disadvantage with this working method. Each floor of the building is generally constructed by laying a steel deck and then casting a floor slab of reinforced concrete on top of the steel deck. Owing to the weight of a typical mobile lift platform and the fact that this weight is concentrated on a rather small area represented by the “footprint” of the wheels, the concrete must be allowed to harden fully before the mobile lift platform can be lifted into position. This may take several days, delaying construction of the building.
Also, the weight of the mobile lift platform is limited by the lifting capacity of the tower crane, which is typically 5000 kg (although cranes with larger lifting capacities are known). This means that only relatively small, lightweight mobile lift platforms can be used.
These problems can be avoided by using a static base lift platform, such as the DR15 platform from Niftylift Limited. This lightweight lift platform has a base unit mounted on a rigid sled comprising two parallel skids, each with a length of approximately 6 meters. These rails spread the weight of the lift platform, allowing it to be placed directly on a steel floor deck, before the reinforced concrete floor slab has been cast. The lift platform can then be used to erect the framework for the next floor, after which it can be lifted onto that floor allowing the concrete to be laid on the previous floor. The construction process can proceed considerably more quickly as a result.
Another benefit of using static base lift platforms is that they tend to be lighter than similarly sized mobile lift platforms. This permits a lighter steel frame structure to be designed into the building, allowing for more efficient design, lower material content and reduced costs.
Although static base lift platforms provide significant advantages over mobile lift platforms in this situation, one disadvantage is that they generally have little use after the main framework of the building has been constructed. They therefore lack the flexibility of mobile lift platforms and have to be transported away from the building site for use elsewhere, or stored on site causing a significant under use of capital resources.
It is an object of the present invention to provide a lift platform that mitigates at least some of these disadvantages.